Test Characteristics of Faecal Immunochemical Tests (FIT) Compared with Optical Colonoscopy

Abstract

Background Faecal occult blood tests are often the initial test in population-based screening. We aimed to: 1) compare the results of single sample faecal immunochemical tests (FITs) with colonoscopy, and 2) calculate the sensitivity for proximal vs. distal adenomatous polyps or cancer. Methods Individuals scheduled for a colonoscopy were invited to complete a FIT prior to their colonoscopy preparation. FIT results were classified as positive, negative, or invalid. Colonoscopy reports were reviewed and abstracted. Because of product issues, four different FIT manufacturers were used. The test characteristics for each FIT manufacturer were calculated for advanced adenomatous polyps or cancer according to broad reason for colonoscopy (screening or surveillance/diagnostic). Results Of those invited, 1,026 individuals (43.9%) completed their colonoscopy and had a valid FIT result. The overall sensitivity of the FITs (95% confidence intervals) was 0.18 (0.10 to 0.28) and specificity was 0.90 (0.87 to 0.91) for advanced adenomas or cancer. The sensitivity for distal lesions was 0.23 (0.11 to 0.38) and for proximal lesions was 0.09 (0.02 to 0.25). The odds ratio of an individual with a distal advanced adenoma or cancer testing positive was 2.68 (1.20 to 5.99). The two individuals with colorectal cancer tested negative, as did one individual with high-grade dysplasia. Conclusions The sensitivity of a single-sample FIT for advanced adenomas or cancer was low. Individuals with distal adenomas had a higher odds of testing positive than those with proximal lesions or no lesions.

Faecal immunochemical tests versus guaiac faecal occult blood tests: what clinicians and colorectal cancer screening programme organisers need to know

“…In addition, the need for visual interpretation of the results (rather than a numerical result) introduces interobserver variation. Not surprisingly, qualitative FIT differ substantially in performance 30 31…”

“…There is a growing literature indicating important differences in quality and performance across qualitative kit brands 30 31 33. Despite this literature, in the USA, qualitative FIT (mostly marketed as point-of-care tests) are Food and Drug Administration approved while quantitative are not.…”

“…Using the multiplier, the manufacturer's recommended positivity threshold of 100 ng haemoglobin/mL buffer for the OC-Sensor becomes 20 µg haemoglobin/g faeces. The need for standardisation is illustrated in a recent study which used four different qualitative FIT kits, all which defined positive as 50 ng haemoglobin/mL buffer 31. However, the actual haemoglobin concentration detected varied from 6 µg haemoglobin/g faeces to 50 µg haemoglobin/g faeces.…”

Effect of Ambient Temperature Variations on Positivity of Manual Fecal Immunochemical Tests

“…[16] Institutional review board (IRB) approval was obtained for this research. Subjects were paid $20 for participation in the study.…”

“…Participants returned a signed informed consent if interested. [16] The first recruitment package was mailed January 22, 2010 and the last recruitment package was mailed November 22, 2011. Recruitment packages were mailed to 2,336 potential subjects.…”